A print cartridge for an inkjet printing system may include a printhead and an ink supply which supplies ink to the printhead such that properly sequenced ejection of drops of ink from the printhead causes characters or other images to be printed upon a print medium as the print cartridge and the print medium are moved relative to each other. The print cartridge may be supported by a carriage that, in one implementation, traverses the print medium from side-to-side during printing operations or, in another implementation, remains stationary as the print medium is moved during printing operations. Unfortunately, wrongful or improper insertion of a print cartridge into the carriage may be harmful.